A progressive cavity pump usually comprises a helical rotor disposed in a double helical bore. Sealed cavities exist between the surfaces of the rotor and stator, and as the rotor turns, these sealed cavities progress along the length of the pump. Thus fluid entering a forming cavity at one end of the pump is transported the length of the pump until the cavity reaches the other end of the pump. The rotor rotates about a central axis, however no part of the rotor lies on this axis, rather each part of the rotor is spaced from the central axis it orbits. Since a drive means usually generates a rotating output that is coincident with the axis of rotation, a jointed or flexible shaft is used to connect the drive output to the rotor.